1. Field of the Invention
This invention is directed to a method and apparatus for deriving amplitude information from periodic waveforms. More particularly, the invention relates to estimating amplitude information from periodic waveforms by estimating the amplitude of harmonic components filtered from digitized sample sequences of the periodic waveforms.
2. Description of Prior Art
The classical means for extracting the amplitude information has been to rectify the signal, then use peak detection apparatus followed by a low-pass filter. The peak detection process can also be implemented with a digital signal processor. The continuous periodic waveform is digitized by a sampling circuit, and the digital signal processor is programmed to perform the above peak detection process.
Either implementation of the peak detection process requires significant amounts of hardware and/or software to implement. Further, the peak detection process only offers two samples per sinusoidal cycle. Accordingly, in peak detection applications, the designer is trading off accuracy of amplitude information against the number of cycles sampled. For accurate amplitude information, many cycles of the periodic waveform must by used.